Ruining Children's Books/Origin Stories

Through a convoluted series of clicking links and searching Wikipedia, I found out that Sony Pictures Animation, who made Surf's Up and Open Season is producing an adaptation of Cloudy with a Chance of Meatballs, a book that I have fond memories of from elementary school, and you probably do too. The book describes a town called Chewandswallow, where all of the weather is in the form of food. If you're not familiar with this book, ask someone who had a childhood.
I actually became somewhat excited about this, even though I feel a certain apprehension of translating a beautifully drawn children's book to CG. But honestly, this is probably one of the less stylized children's books, and thus is less dependent on being hand-drawn for its feel.
What absolutely enraged me, though, was that they plan to explain the origins of Chewandswallow's weather. I think Patton Oswalt put it best:
"I DON'T GIVE A SHIT WHERE THE STUFF I LOVE COMES FROM! I JUST LOVE THE STUFF I LOVE!"
Why the hell would they ruin a perfectly quirky and magical story with something like an explanation? Isn't what makes books like this so memorable the fact that it's so matter-of-fact about the situation, and it lets the kids escape to a world that is at once familiar to their own, yet completely alien from it? The book never asked kids to become the wet blanket in their first-grade class and ask "But teacher, how is such a town possible? Ground beef and soup don't occur naturally." Creating an origin story would just ruin this perfect fantasy because providing an explanation for the town would indicate that something had to make it that way, instead of the much more fun idea that that's just how things always were.
Come to think of it, why are producers/writers so enthralled with origin stories? As far as movies go, the only origin stories I've seen that I liked significantly and actually added something to the character/story were Batman Begins, Iron Man, and Indiana Jones and the Last Crusade. And even in those cases, one had ninjas, one had Robert Downey Jr., and one had a kickass chase scene and beautiful scenery. Well, what actually made the former two stories good , particularly in the realm of superhero origins, is that they were the rare self-made superheroes. Unlike most of Stan Lee's lazy "something radioactive happened" or "born that way" origins, in these cases character development --> superpowers instead of superpowers --> character development. Most of the time, again particularly in comic book movies, an origin story is a writer's easy way to fill 40 minutes without having to worry about a plot yet.
The fact is most of the time, not only do we not care how someone or something was created or became they way they are in the present, but often the presentation of an origin actually ruins the already established story *cough*starwarsprequels*cough*. Most filmmakers today seem to have forgotten that people like a little mystery, because they to fill in the blanks themselves. Darth Vader and Boba Fett were way cooler before I was spoon-fed the whole story about how they were kids with single parents (for a lack of a better word for the relationship between Jango and Boba Fett). That one shot in Empire Strikes Back when you saw the back of Vader's gross pink head, and then at the end of Return of the Jedi when you saw his gross pink face, were awesome because they pushed the question about what horrible event led to his condition. People were able to use their *gasp!* imaginations to answer it. More importantly, before Episode III spelled it out for us in the form of "He had a fight with Obi-Wan and he fell in some lava and caught on fire", it was easier to accept this condition as metaphorical; a visualization of how the Dark Side had corrupted him, and probably a thousand other metaphors depending on who you ask.
Fiction, particularly fantastic stories like surreal children's books, fantasy in its varying forms, and science fiction, is so great because the best of its storytellers are able to create a world that you can become immersed in and begin to believe in, with characters that you can feel like they exist on some other plane, and can imagine interacting with the world they live in.
The best worlds and characters in fiction already feel like they have lived a life/existence before the story began; you don't need to make up the whole life.

Say you have a black box with a bunch of white gaps in a checkerboard-like pattern. Now fill in all of the white with black. What's more interesting, the black-and-white block with the gaps, or the solid black box, with all of the gaps filled in?